WeiKang Zheng
A5064846706- Gamma-ray bursts and supernovae
- Astrophysical Phenomena and Observations
- Pulsars and Gravitational Waves Research
- Stellar, planetary, and galactic studies
- Astrophysics and Cosmic Phenomena
- Astronomy and Astrophysical Research
- Astro and Planetary Science
- Astronomical Observations and Instrumentation
- Galaxies: Formation, Evolution, Phenomena
- SAS software applications and methods
- Neutrino Physics Research
- Optical Systems and Laser Technology
- Radio Astronomy Observations and Technology
- Adaptive optics and wavefront sensing
- Astrophysics and Star Formation Studies
- Geophysics and Gravity Measurements
- Medical Imaging Techniques and Applications
- Nuclear Physics and Applications
- Particle Accelerators and Free-Electron Lasers
- Particle Detector Development and Performance
- Geological and Geophysical Studies
- Advanced Research in Systems and Signal Processing
- Atomic and Molecular Physics
- Power Systems and Technologies
- Particle physics theoretical and experimental studies
University of California, Berkeley
2015-2024
City University of Hong Kong
2024
University of Michigan–Ann Arbor
2010-2024
LEO Foundation
2023
Karolinska University Hospital
2023
Karolinska Institutet
2023
Turku Centre for Computer Science
2023
University of Turku
2023
Miller College
2023
Astronomy and Space
2023
We report observations from HST of Cepheids in the hosts 42 SNe Ia used to calibrate Hubble constant (H0). These include all suitable last 40 years at z<0.01, measured with >1000 orbits, more than doubling sample whose size limits precision H0. The are calibrated geometrically Gaia EDR3 parallaxes, masers N4258 (here tripling that Cepheid sample), and DEBs LMC. were same WFC3 instrument filters (F555W, F814W, F160W) negate zeropoint errors. present multiple verifications photometry tests...
Abstract We present Hubble Space Telescope (HST) photometry of a selected sample 50 long-period, low-extinction Milky Way Cepheids measured on the same WFC3 F 555 W -, 814 and 160 -band photometric system as extragalactic in Type Ia supernova host galaxies. These bright were observed with spatial scanning mode optical near-infrared to mitigate saturation reduce pixel-to-pixel calibration errors reach mean error 5 mmag per observation. use new Gaia DR2 parallaxes HST simultaneously constrain...
Here we present 1701 light curves of 1550 spectroscopically confirmed Type Ia supernovae (SNe Ia) that will be used to infer cosmological parameters as part the Pantheon+ SN analysis and SH0ES (Supernovae H0 for Equation State dark energy) distance-ladder analysis. This effort is one a series works perform an extensive review redshifts, peculiar velocities, photometric calibration, intrinsic-scatter models SNe Ia. The total number curves, which are compiled across 18 different surveys,...
Abstract We describe Keck-telescope spectrophotometry and imaging of the companion “black widow” pulsar PSR J0952−0607, fastest known spinning neutron star (NS) in disk Milky Way. The is very faint at minimum brightness, presenting observational challenges, but we have measured multicolor light curves obtained radial velocities over illuminated “day” half orbit. model fits indicate system inclination i = 59.°8 ± 1.°9 a mass M NS 2.35 0.17 ⊙ , largest well-measured found to date. Modeling...
We present multiwavelength observations of the afterglow GRB 130427A, brightest (in total fluence) gamma-ray burst (GRB) past 29 yr. Optical spectroscopy from Gemini-North reveals redshift to be z = 0.340, indicating that its unprecedented brightness is primarily result relatively close proximity Earth; intrinsic luminosities both and are not extreme in comparison other bright GRBs. a large suite spanning 300 s 130 days after demonstrate shows simple, smooth evolution at all frequencies,...
We report observations from HST of Cepheids in the hosts 42 SNe Ia used to calibrate Hubble constant (H0). These include all suitable last 40 years at z<0.01, measured with >1000 orbits, more than doubling sample whose size limits precision H0. The are calibrated geometrically Gaia EDR3 parallaxes, masers N4258 (here tripling that Cepheid sample), and DEBs LMC. were same WFC3 instrument filters (F555W, F814W, F160W) negate zeropoint errors. present multiple verifications photometry...
Abstract We present ultraviolet/optical/near-infrared observations and modeling of Type II supernovae (SNe II) whose early time ( δ t < 2 days) spectra show transient, narrow emission lines from shock ionization confined r 10 15 cm) circumstellar material (CSM). The observed electron-scattering broadened line profiles (i.e., IIn-like) H i , He i/ii C iv N iii/iv/v the CSM persist on a characteristic timescale IIn ) that marks transition to lower-density emergence Doppler-broadened...
ABSTRACT We present ground-based optical photometric monitoring data for NGC 5548, part of an extended multiwavelength reverberation mapping campaign. The light curves have nearly daily cadence from 2014 January to July in nine filters ( BVRI and ugriz ). Combined with ultraviolet the Hubble Space Telescope Swift , we confirm significant time delays between continuum bands as a function wavelength, extending wavelength coverage 1158 Å z band (~9160 Å). find that lags at wavelengths longer...
ABSTRACT OJ 287 is a quasi-periodic quasar with roughly 12 year optical cycles. It displays prominent outbursts that are predictable in binary black hole model. The model predicted major outburst 2015 December. We found the did occur within expected time range, peaking on December 5 at magnitude 12.9 R -band. Based Swift /XRT satellite measurements and polarization data, we find it included thermal component. Its timing provides an accurate estimate for spin of primary hole, . present also...
SN 2014J in M82 is the closest detected Type Ia supernova (SN Ia) at least 28 years and perhaps 410 years. Despite its small distance of 3.3 Mpc, surprisingly faint, peaking V = 10.6 mag, assuming a typical luminosity, we infer an observed visual extinction A_V 2.0 +/- 0.1 mag. But this picture, with R_V 1.6 0.2, too simple to account for all observations. We combine 10 epochs (spanning month) HST/STIS ultraviolet through near-infrared spectroscopy HST/WFC3, KAIT, FanCam photometry from...
We have obtained early-time photometry and spectroscopy of supernova (SN) 2013df in NGC 4414. The SN is clearly Type IIb, with notable similarities to 1993J. From its luminosity at secondary maximum light, it appears that less 56Ni (≲ 0.06 M☉) was synthesized the explosion than case for SNe IIb 1993J, 2008ax, 2011dh. Based on a comparison light curves, progenitor must been more extended radius prior total extinction estimated be AV = 0.30 mag. metallicity location likely solar. conducted...
ABSTRACT We report evidence for excess blue light from the Type Ia supernova (Sn Ia) SN 2012cg at 15 and 16 days before maximum B -band brightness. The emission is consistent with predictions impact of on a non-degenerate binary companion. This first companion to normal Ia. Sixteen light, <?CDATA $B-V$?> <?MML <mml:math> <mml:mi>B</mml:mi> <mml:mo>−</mml:mo> <mml:mi>V</mml:mi> </mml:math>?> color 0.2 mag bluer than other At later times, this has typical curve, extinction-corrected...
We present multi-wavelength observations of the tidal disruption event (TDE) iPTF15af, discovered by intermediate Palomar Transient Factory (iPTF) survey at redshift $z=0.07897$. The optical and ultraviolet (UV) light curves transient show a slow decay over five months, in agreement with previous optically TDEs. It also has comparable black-body peak luminosity $L_{\rm{peak}} \approx 1.5 \times 10^{44}$ erg/s. inferred temperature from UV data shows value (3$-$5) $\times 10^4$ K. is not...
Abstract We present observations of SN 2021csp, the second example a newly identified type supernova (SN) hallmarked by strong, narrow, P Cygni carbon features at early times (Type Icn). The appears as fast and luminous blue transient times, reaching peak absolute magnitude −20 within 3 days due to strong interaction between ejecta ( v ≈ 30,000 km s −1 ) massive, dense, fast-moving C/O wind shed WC-like progenitor months before explosion. narrow-line disappear from spectrum 10–20 after...
We present multiwavelength observations of the Type II SN 2020pni. Classified at $\sim 1.3$ days after explosion, object showed narrow (FWHM $<250\,\textrm{km}\,\textrm{s}^{-1}$) recombination lines ionized helium, nitrogen, and carbon, as typically seen in flash-spectroscopy events. Using non-LTE radiative transfer code CMFGEN to model our first high resolution spectrum, we infer a progenitor mass-loss rate $\dot{M}=(3.5-5.3)\times10^{-3}$ M$_{\odot}$ yr$^{-1}$ (assuming wind velocity...
We carried out spectroscopic monitoring of 21 low-redshift Seyfert 1 galaxies using the Kast double spectrograph on 3-m Shane telescope at Lick Observatory from April 2016 to May 2017. Targeting active galactic nuclei (AGN) with luminosities {\lambda}L{\lambda} (5100 {\AA}) = 10^44 erg/s and predicted H{\beta} lags 20-30 days or black hole masses 10^7-10^8.5 Msun, our campaign probes luminosity-dependent trends in broad-line region (BLR) structure dynamics as well improve calibrations for...
ABSTRACT The most stringent local measurement of the Hubble–Lemaître constant from Cepheid-calibrated Type Ia supernovae (SNe Ia) differs value inferred via cosmic microwave background radiation (Planck+ΛCDM) by ∼5σ. This so-called Hubble tension has been confirmed other independent methods, and thus does not appear to be a possible consequence systematic errors. Here, we continue upon our prior work using II provide another, largely method measure constant. From 13 SNe with geometric,...
Abstract We present six epochs of optical spectropolarimetry the Type II supernova (SN) 2023ixf ranging from ∼2 to 15 days after explosion. Polarimetry was obtained with Kast double spectrograph on Shane 3 m telescope at Lick Observatory, representing earliest such observations ever captured for an SN. observe a high continuum polarization p cont ≈ 1% +1.4 and +2.5 before dropping 0.5% day +3.5, persisting that level up +14.5. Remarkably, this change coincides temporally disappearance highly...
Abstract We follow our first paper with an analysis of the ensemble extensive preexplosion ground- and space-based infrared observations red supergiant (RSG) progenitor candidate for nearby core-collapse supernova SN 2023ixf in Messier 101, together optical data prior to explosion obtained Hubble Space Telescope (HST). have confirmed association (SN), as well constrained metallicity at site, based on instruments Gemini-North. The internal host extinction has also been from a high-resolution...
Capacitive deionization (CDI) has emerged as a promising technology for freshwater recovery from low-salinity brackish water. It is still inapplicable in specific scenarios (e.g., households, islands, or offshore platforms) due to too low volumetric adsorption capacities. In this study, high-density semi-metallic molybdenum disulfide (1T'-MoS
The Type Ia supernova (SN Ia) 2013dy in NGC 7250 (d ~ 13.7 Mpc) was discovered by the Lick Observatory Supernova Search. Combined with a prediscovery detection Italian Search Project, we are able to constrain first-light time of SN be only 0.10 +/- 0.05 d (2.4 1.2 hr) before first detection. This makes earliest known an Ia. We infer upper limit on radius progenitor star R_0 < 0.25 R_sun, consistent that white dwarf. light curve exhibits broken power law exponents 0.88 and then 1.80. A...
Long-duration gamma-ray bursts (GRBs) at z < 1 are found in most cases to be accompanied by bright, broad-lined Type Ic supernovae (SNe Ic-BL). The highest-energy GRBs mostly located higher redshifts, where the associated SNe hard detect observationally. Here, we present early and late observations of optical counterpart very energetic GRB 130427A. Despite its moderate redshift, = 0.3399 ± 0.0002, 130427A is high end energy distribution, with an isotropic-equivalent release Eiso ∼ 9.6 × 1053...